Study On The Withdrawal Time Of Methimazole Before ¹³¹I Treatment Of Graves’ Disease

OBJECTIVE:The treatment of Graves’disease（GD）is the preferred anti-thyroid drug（ATDs）in China,with Methimazole（MMI）as the preferred oral medications,MMI can be used for pretreatment of Radioiodine Treatment（RIT）or surgical treatment.However,there was no consensus at home and abroad about the withdrawal time of MMI before RIT.The purpose of this study was to investigate the response of methimazole（MMI）to radioactive iodine treatment（RIT）at different withdrawal times in order to arrive at the optimal withdrawal time of MMI before RIT.RESEAERCH METHODS:We randomly selected 180 patients with Graves’disease who received RIT from Jun.2016 to Dec.2017 in the nuclear medicine clinic of China-Japan Union Hospital of Jilin University,according to FT3、FT4 within or not the normal range are divided into I group and II group.FT3 and FT4 are within the normal range was group I and FT3 and FT4 are not within the normal range was group II.According to MMI withdrawal time are divided into 1≤t≤3days（Ia subgroup and IIa subgroup）,3<t≤7days（Ib subgroup and IIb subgroup）,7<t≤14days（Ic subgroup and IIc group）.Each patient was randomly assigned to a different subgroup.Thyroid weight was calculated in the light of thyroid ultrasound,depending on Quimby calculation formula to obtain the required ¹³¹I dose with a dose of 100uCi of ¹³¹I per gram of thyroid weight.The effect of treatment was evaluated at 1,3 and 6 months after RIT.Normal thyroid function and hypothyroidism were regard as effective,conversely,the treatment of hyperthyroidism was invalid.RESEAERCH RESULTS:The overall effective rate was 46.6%（82/176）.In group I,there were 8 patients with normal thyroid function and 31 patients with hypothyroidism,with an effective rate of44.8%（39/87）.There was no significant difference in response to treatment with Ia、Ib、Ic group at 1,3,6months after RIT（P>0.05）.Similarly,11 patients with normal thyroid function and 32 patients with hypothyroidism had an effective rate of 48.3%（43/89）in group II.There was no significant difference in response to treatment withI Ia、IIb、IIc group at 1,3,6months after RIT（P>0.05）.There was also no significant difference in response to treatment withI I and II group at 6months after RIT（P>0.05）.Multivariate Logistic regression analysis was used to observe the independent risk factors influencing RIT,including duration of disease,MMI dose,24-hour iodine uptake rate,thyroid volume,¹³¹I dose,FT4,and TRAb,showing that the age and thyroid volume were the influence factors of RIT（P<0.05）.CONCLUSION:There was no difference in responce to RIT at three different withdrawal points of MMI.Because of the longer MMI withdrawal time,serum FT4 more increased,the symptoms and complications of hyperthyroidism was possible more aggravated.Therefore,it is recommended to stop MMI for 1-3 days before RIT.